During the last school year, Michigan had the fourth-highest rate of vaccine waivers in the nation, according to information released last week by the Centers for Disease Control and Prevention. That means 5.5%, or roughly 7,300, of the state’s kindergartners skipped vaccinations for religious or philosophical reasons, up from 5,700 during the 2010-11 school year.

Vaccines have been an established part of disease prevention for centuries, but a 1998 study that claimed to have found a link between autism and a commonly given vaccine that protects against measles, mumps and rubella started a worldwide vaccine panic. That study has been thoroughly discredited: 12 of its 13 authors have renounced it, and the medical journal that published the study has retracted it.

An analysis by a British journalist found that hospital records presented in the study had been altered or misrepresented. Namely, many of the children in whom vaccines had supposedly caused autism had been diagnosed with developmental difficulties prior to administration of the vaccine. And the study’s lead doctor was stripped of his medical license after an investigation found that he had behaved unethically.

Yet parents continue to refuse vaccinations.

And as a result, some illnesses once thought close to eradication are making a return — deadly diseases such as measles and whooping cough are afflicting children in increasing numbers, with some 850 cases of whooping cough in Michigan alone last year.

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Like most states, Michigan requires children to receive vaccinations against common, preventable illnesses —such as measles, whooping cough, polio, chicken pox and meningitis — before attending public or private school. But Michigan is one of 48 states that allows parents to request waivers for religious reasons, and one of about 20 that allows exemptions for philosophical reasons.

It’s bad enough that parents who decide against vaccinating are taking deadly risks with their own children. But failing to vaccinate a child threatens others, too. Some children and adults with depressed immune systems can’t be vaccinated. Very young infants are inoculated on a schedule; vaccine protection layers in over the first year of a child’s life. And vaccines work differently for different people. Most people develop a robust immunity that’s successful in warding off illness. But for a small percentage, the vaccine doesn’t work as well.

This is why herd immunity — the idea that a group of vaccinated individuals is less likely to contract and spread the diseases they’re vaccinated against — is so important. There’s also some risk that a disease can mutate into a vaccine-resistant strain; the best defense against that kind of mutation, scientists say, is to decrease or eradicate instances of the disease before it has time to mutate.

If parents insist on opting out of life-saving inoculations — and this is a public health concern, not a personal choice — the state Legislature should start by tightening the requirements for exemptions. It’s a small price to pay to keep deadly illnesses like whooping cough, measles and smallpox part of our past.